Characterization of fluids within an oilfield reservoir is desirable, if not necessary, for many reasons. For example, the behavior of a fluid within the reservoir depends upon its composition. Modeling this behavior with time typically requires the results of compositional analyses along with the knowledge of other physical parameters. Proper reservoir management requires the knowledge of reservoir conditions, such as pressure, temperature, and the like, in addition to the composition of the fluid within the reservoir. During transportation and storage, the mixing of different fluids can cause perturbation of the fluids system. The presence of incompatible fluids can lead to precipitation and deposition of such precipitates on components of the fluid transportation system. The refining process is also dependent upon the nature and makeup of the reservoir fluids being refined. To characterize such reservoir fluids, the fluids are commonly separated into saturates, aromatics, resins, and asphaltenes, or “SARA” fractions.
Conventional methods employed to separate reservoir fluids into these fractions require large quantities of solvents, are time consuming and operator dependent, and are not practical to use in the field. Such conventional methods typically require a significant inventory of tools and glassware, including evaporators and a fume hood. Moreover, equipment required to perform these conventional methods occupies a large footprint, which limits the mobility of the technique. Furthermore, cross-contamination is common, wherein one fraction is not completely separated, resulting in contamination of other fractions. Conventional separation methods also suffer from poor repeatability and reproducibility.